LED Bulb

ABSTRACT

An LED bulb includes: a circuit board having opposite first and second surfaces; a plurality of LEDs disposed on the first surface; and a heat dissipating structure having a heat dissipating board, wherein the heat dissipating board has opposite third and fourth surfaces, the third surface is attached to the second surface of the circuit board, and a plurality of heat dissipating bumps is disposed on the fourth surface and gradually decreases in length from the center toward the periphery of the fourth surface to thereby facilitate air convection around the heat dissipating bumps, thus improving the overall heat dissipating efficiency so as to increase the light emitting efficiency and lifetime of the LED bulb.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 13/010,746 filedJan. 20, 2011, which application claims the benefit of foreign priorityof TW 099135907 filed Oct. 21, 2010.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to light emitting diode (LED) bulbs, andmore particularly, to an LED bulb having a heat dissipating structuredisposed therein.

2. Description of Related Art

Since LEDs have advantages of long lifetime, low power consumption andshort response time and do not have idling time, the application of theLEDs is increasingly expanded. Particularly, white LEDs are being widelyadopted in lighting applications, and conventional halogen orincandescent bulbs are being replaced by the LEDs so as to meet theenergy saving and carbon reducing trend.

FIG. 1 is a perspective view of an LED bulb disclosed by Taiwan UtilityModel Patent No. M389826. Referring to FIG. 1, the LED bulb 1 comprisesa light-transmittable cover 11 with a globe shape, a base 12, and anelectrical contact 13. A plurality of light source circuit components,such as LEDs, a circuit board and a transformer (not shown), is disposedinside the base 12 and the cover 11. A heat dissipating structurecomprising a plurality of fins 120 each having a plurality of heatdissipating holes 121 is disposed around the periphery of the base 12such that heat generated by the light source circuit components can bedissipated to the outside through the fins 120. The heat dissipatingeffect can further be improved by convection through the heatdissipating holes 121.

However, since heat is generated inside the bulb while the heatdissipating structure of the bulb is disposed around the periphery ofthe base 12 and thermal convection through the heat dissipating holes121 only reaches the surface of the base 12, the heat cannot beeffectively and rapidly dissipated by the heat dissipating structure,thus resulting in high temperature of the bulb. Further, the hightemperature of the bulb can adversely affect the light emittingefficiency of the LEDs, cause rapid deterioration of the circuit board,and shorten the lifetime of the bulb.

Therefore, it is imperative to provide an LED bulb with improved heatdissipating efficiency so as to increase the light emitting efficiencyand lifetime of the LED bulb.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides an LED bulb, whichcomprises: a circuit board having a first surface and a second surfaceopposite to the first surface; a plurality of LEDs disposed on the firstsurface of the circuit board; and a heat dissipating structure having aheat dissipating board, wherein the heat dissipating board has a thirdsurface and a fourth surface opposite to the third surface, the thirdsurface is attached to the second surface of the circuit board, and aplurality of heat dissipating bumps is disposed on the fourth surfaceand gradually decreases in length from the center toward the peripheryof the fourth surface.

In an embodiment of the present invention, the LED bulb can furthercomprise a housing disposed around the circuit board and the heatdissipating structure and having a plurality of openings disposedtherein and positioned around the heat dissipating bumps.

In an embodiment of the present invention, the housing can have a heatdissipating space formed near the LEDs that generate heat, the heatdissipating structure being disposed in the heat dissipating space.

In an embodiment of the present invention, the fourth surface of theheat dissipating board can have a protruding portion with a heightgradually decreasing from the center toward the periphery of the fourthsurface.

In an embodiment of the present invention, the heat dissipatingstructure can be made of metal.

In an embodiment of the present invention, the heat dissipatingstructure can be formed by die casting.

In an embodiment of the present invention, the heat dissipating bumpscan have a triangular pyramid shape, a square pyramid shape, a polygonalpyramid shape, a triangular tapered column shape, a square taperedcolumn shape, a polygonal tapered column shape, a round column shape, asquare column shape or a polygonal column shape.

In an embodiment of the present invention, the LED bulb can furthercomprise a nano-scaled radiation coating disposed on the heatdissipating bumps.

According to the present invention, the heat dissipating bumps thatgradually decrease in length from the center toward the periphery of thefourth surface facilitate rapid dissipation of hot air in the center andthe openings disposed around the heat dissipating structure also help todissipate heat, thereby maintaining the LED bulb at a normal temperatureso as to increase the light emitting efficiency and lifetime of the LEDbulb.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 (PRIOR ART) is perspective view of a conventional LED bulb;

FIGS. 2A and 2B are an exploded view and an assembly view, respectively,of an LED bulb according to the present invention;

FIG. 3 is a side view showing an embodiment of a heat dissipatingstructure of the LED bulb according to the present invention; and

FIG. 4 is a side view showing another embodiment of the heat dissipatingstructure of the LED bulb according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following embodiments are provided to illustrate the presentinvention. Those skilled in the art will readily understand otheradvantages and functions of the present invention in accordance with thecontents disclosed in this specification.

FIGS. 2A and 2B are an exploded view and an assembly view, respectively,of an LED bulb 2 according to the present invention.

Referring to FIGS. 2A and 2B, the LED bulb 2 comprises: a circuit board21 having a first surface 21 a and a second surface 21 b opposite to thefirst surface 21 a; a plurality of LEDs 22 disposed on the first surface21 a; and a heat dissipating structure 23 comprising a heat dissipatingboard 231, wherein the heat dissipating board 231 has a third surface231 a and a fourth surface 231 b opposite to the third surface 231 a,the third surface 231 a of the heat dissipating board 231 is attached tothe second surface 21 b of the circuit board 21, and the fourth surface231 b of the heat dissipating board 231 has a plurality of heatdissipating bumps 232 disposed thereon. Further, as shown in FIG. 3,which is a side view of the heat dissipating structure 23, the heatdissipating bumps 232 gradually decrease in length from the centertoward the periphery of the fourth surface 231 b.

In an embodiment of the present invention, the above-described heatdissipating structure 23 can be formed by die casting.

In an embodiment of the present invention, the above-described LED bulbfurther comprises a housing 24 disposed around the circuit board 21 andthe heat dissipating structure 23, and a plurality of openings 240 isdisposed in the housing 24 and positioned around the heat dissipatingbumps 232. In particular, a heat dissipating space 28 is formed near theLEDs 22 that generate heat, and the heat dissipating structure 23 isreceived in the heat dissipating space 28. In an embodiment of thepresent invention, the heat dissipating structure 23 is preferably madeof metal, and the third surface 231 a of the heat dissipating board 231is attached to the second surface 21 b of the circuit board 21preferably through a thermal paste so as to improve the heat conductingefficiency.

Referring to FIG. 2A, the edges of the circuit board 21 and the heatdissipating structure 23 engage with a groove 241 inside the housing 24,and another groove 242 disposed on the outside of the housing 24 engageswith the edge of a cover 25, thereby facilitating the assembly of theLED bulb and saving cost. The cover 25, a power driver 26 and anelectrical contact 27 shown in FIGS. 2A and 2B can be provided as knownin the prior art, and accordingly detailed description thereof isomitted herein.

According to the above-described structure, heat generated by thecircuit board 21 and the LEDs 22 is conducted to the heat dissipatingbumps 232 of the heat dissipating structure 23. Since the heatdissipating bumps 232 located in the center of the heat dissipatingstructure 23 are longer than the heat dissipating bumps 232 locatedaround the periphery of the heat dissipating structure 23, the heatdissipating bumps 232 located in the center of the heat dissipatingstructure 23 have a larger heat dissipating area for effectivelydissipating heat in the center of the circuit board 21, and the shorterheat dissipating bumps 232 located around the periphery of the heatdissipating structure 23 will not block the flow of air in the center.As such, heat in the center can be rapidly dissipated by the heatdissipating bumps 232 through air convection. Furthermore, the openings240 disposed in the housing 24 cause hot air to be rapidly dissipatedout of the LED bulb 2 in all directions (360 degrees), therebyincreasing the heat dissipating efficiency.

FIG. 4 shows another embodiment of the heat dissipating structureaccording to the present invention. For purpose of simplification, onlythe difference of the present embodiment from the previous embodiment ofFIG. 3 is described herein. Referring to FIG. 4, the heat dissipatingboard 231′ of the heat dissipating structure 23′ has a protrudingportion 2311 with a height gradually decreasing from the center towardthe periphery of the fourth surface 231 b′ so as to increase the heatdissipating area.

In the LED bulb of the present invention, the heat dissipating bumps 232can have, but not limited to, a triangular pyramid shape, a squarepyramid shape, a polygonal pyramid shape, a triangular tapered columnshape, a square tapered column shape, a polygonal tapered column shape,a round column shape, a square column shape or a polygonal column shape.

In addition, the present invention can comprise a nano-scaled radiationcoating that is disposed on heat dissipating bumps 232 through spraycoating, for example, so as to further improve the heat dissipatingefficiency.

Therefore, the housing of the LED bulb of the present invention has aheat dissipating space formed near the LEDs that generate heat forreceiving a heat dissipating structure, wherein the heat dissipatingstructure comprises a heat dissipating board having one surface attachedto the circuit board having the LEDs and the other surface having aplurality of heat dissipating bumps disposed thereon and graduallydecreasing in length from the center toward the periphery of the heatdissipating board. The heat dissipating bumps that gradually decrease inlength from the center toward the periphery of the heat dissipatingboard facilitate rapid dissipation of hot air in the center and theopenings disposed around the heat dissipating structure also help todissipate heat. Further, the heat dissipating space, the heatdissipating bumps and the openings disposed in the housing facilitatethermal convection. As such, the overall heat dissipating effect isimproved so as to maintain the LED bulb at a normal temperature, therebyincreasing the light emitting efficiency and lifetime of the LED bulb.

The above-described descriptions of the detailed embodiments areintended to illustrate the preferred implementation according to thepresent invention but are not intended to limit the scope of the presentinvention. Accordingly, all modifications and variations completed bythose with ordinary skill in the art should fall within the scope ofpresent invention defined by the appended claims.

1. An LED bulb, comprising: a circuit board having a first surface and a second surface opposite to the first surface; a plurality of LEDs disposed on the first surface of the circuit board; and a heat dissipating structure having a heat dissipating board, wherein the heat dissipating board has a third surface and a fourth surface opposite to the third surface, the third surface is attached to the second surface of the circuit board, and a plurality of heat dissipating bumps are disposed on the fourth surface; a cover engaged on top of a housing to form the closed LED bulb, wherein the cover has no opening on the top, wherein the LEDs are positioned upwards and covered by the cover; and said housing disposed around the circuit board and the heat dissipating structure, wherein the housing has a plurality of openings positioned around the heat dissipating structure in such a way as to draw the heat away from the LEDs on the circuit board through the heat dissipating structure and out of the heat dissipating space through the openings in the housing via air convection in all directions. 